1. Field:
The present disclosure relates generally to input signal detection circuits and, more specifically, to digital circuits for detecting a peak value of an input signal.
2. Discussion of the Related Art:
Many electronic devices, such as cell phones, laptop computers, etc., use direct current (dc) power to operate. Conventional wall outlets generally deliver a high-voltage alternating current (ac) power that needs to be transformed to dc power in order to be used as a power source by most electronic devices. Switched mode power converters are commonly used to transform ac power to dc power due to their high efficiency, small size, and low weight. In operation, a switched mode power converter may use a controller to control the switching (turning on and turning off) of a power switch to provide a desired output to a load. The controller may regulate the output at a desired level in response to a feedback signal representative of the output of the power converter. The controller may also provide power factor correction (PFC) to improve the power factor of the power converter.
The power factor may be defined as the ratio of the average power over a cycle to the product of the root mean square (rms) voltage and the rms current. That is, the power factor may represent the ratio of the amount of usable power to the amount of total power delivered to the load. As such, the power factor may have a value between zero and one, with unity power factor being the ideal.
A controller of a switched mode power converter may perform PFC in an attempt to achieve unity power factor, typically by shaping the input current waveform as closely as possible to the input voltage waveform. A controller that performs PFC may receive an input signal that is representative of a voltage signal produced by the high-voltage ac power source. The high-voltage ac power source may typically produce a cyclic voltage signal, such as, for example, a sine wave. The peak value of each cycle of the voltage signal or, in other words, the peak value of the input signal per each cycle, may be used by the controller for a variety of purposes, including controlling the switching of the power switch. The peak value of the input signal may increase or decrease from cycle to cycle.